Stabilized light source for operation at substantially constant temperature and intensity



S. H. BOLAND July 22, 1969 3,457,454 TIALLY STABILIZED LIGHT SOURCE FOR OPERATIONAT SUBSTAN CONSTANT TEMPERATURE AND INTENSITY Filed Aug. 1. 1966 rnlll Pan/El? SOURCE Y 29 //Vl//VTOR.

5T5 vz/v H. BOLHNO BY HIS HTTOR/VL'YS. 33 HARP/.5, K/ECH, RusscLL 62 KER/V United States Patent US. Cl. 315-115 6 Claims ABSTRACT OF THE DISCLOSURE A stable light source including a glow discharge lamp such as a mercury vapor lamp positioned within a metal block, a heater for the metal block, and a heater control for maintaining the temperature of the block intermediate the temperature of the lamp and the ambient temperature for lamp operation at a high constant temperature.

This invention relates to light sources of substantially constant intensity and, in particular, to sources utilizing glow discharge lamps, such as mercury vapor and argon lamps and the like.

It is an object of the invention to provide a light source having a higher intensity output and one of substantially constant intensity. The intensity of the emission from a lamp varies with the lamp temperature and with higher temperature lamps, more problems are encountered with lamp temperature control. At the present time it is desirable to utilize higher lamp temperatures for higher outputs and also for use with different gases and vapors in the lamp.

It is an object of the invention to provide a new and improved stabilized light source adapted for operation of the lamp at an elevated and substantially constant temperature. A further object is to provide a new and improved light source incorporating means for controlling heat losses from the structure.

It is an object of theinvention to provide a stabilized light source including a lamp mounted in a metal block for heat transfer from the lamp to the block and from the block to the ambient atmosphere, with the block incorporating another heat source for maintaining the block at a substantially constant temperature.

It is a particular object of the invention to provide a stable light source for producing radiation at substantially constant intensity and including a glow discharge lamp, a metal mounting block having a lamp opening therein with the lamp positioned in the lamp opening, with the block including a light passage communicating with the lamp opening for radiation from the lamp to the exterior of the block, a heater for the block, and heater control means including temperature responsive means carried on the block, with the control means maintaining the temperature of the block adjacent the temperature responsive means substantially at a predetermined value intermediate that of the lamp and that of the ambient atmosphere. An additional object is to provide such a device wherein the mounting block also serves as a stable temperature reference for the heater control means.

It is an object of the invention to provide a lamp structure adapted for use in a stabilized light source and comprising a glow discharge lamp having a lamp body and a baseand an outer sleeve disposed about and spaced from the lamp body and carried on the base providing a closed space around the lamp body.

The invention "also comprises novel details of construction and novel combinations and arrangements of parts, which will more fully appear in the course of the following description. The drawing merely shows and the description merely describes a preferred embodiment of the present invention which is given by way of illustration or example.

In the drawing:

FIG. 1 is a perspective view of a preferred form of the stable light source of the invention;

FIG. 2 is an enlarged side view of the device of FIG. 1 with a cover removed;

FIG. 3 is an enlarged partial sectional view taken along the line 3-3 of FIG. 1;

FIG. 4 is a partial sectional view taken along the line 44 of FIG. 3; and

FIG. 5 is an enlarged partial sectional view of a preferred form of the lamp structure of the invention.

In the preferred embodiment illustrated in the drawing, the light source is mounted in a box 10 having a removable cover 11. A flange 12 on the bottom surface of the box provides for supporting the box on a vertical post 13. Of course, any convenient mounting means may be utilized.

A metal mounting block 20, typically of aluminum, is positioned within the box 10, and preferably is supported on plastic spacer members 21 (FIG. 4) so as to have no direct contact with the box. A lamp 25 is positioned in a lamp opening 26 in the block 20 and a passage 27 provides 'a light path from the lamp to the exterior of the block. A window 28, typically of quartz, may be provided at the passage 27 for the purpose of keeping atmospheric contaminants away from the lamp and for the purpose of blocking ambient air flow directly onto the lamp. A mounting bracket 29 may be provided on the exterior of the box 10 and aligned with the passage 27 for supporting filters or the like, as desired.

A heat source is provided for the mounting block 20 and is operated to maintain the temperature of the block substantially constant. The temperature setting for the block is selected to fall between the temperature of the lamp 25 and the temperature of the ambient atmosphere, with the block temperature preferably being maintained in the range of about 15 to 25 F. below that of the lamp. In a typical unit utilizing a mercury-argon lamp, the lamp temperature is about 125 F. and the block temperature in the area between the lamp and the heat source is about 105 F., with the ambient temperature being about F.

Typically the heat source may be a conventional electric resistance heater utilizing a conventional control circuit for energizing the heater from a power source 30. Various circuits for this purpose are known and none will be shown in detail herein. The control circuit 31 may be mounted on a circuit board 35 mounted on a side of the block 20 by screws 36. The heating element 37 preferably is positioned in an opening 38 centrally located in the block 20, providing for maximum heat transfer. The control circuit will include a temperature responsive element, typically a varistor 32, which may be mounted in an opening 39 in the block 20. Temperature stabilization of the control circuit may be improved by mounting any temperature sensitive elements therein, typically transistors 33, in the block 20, such as in openings 40, 41.

Forced air cooling may be incorporated in the structure, as by means of cooling fins 44 carried on the block 20 and projecting into an open air space 45 within the box 10. Openings may be provided in the lower and upper portions of the boX adjacent the fins 44, permitting upward flow of air over the fins. Air flow will occur as a result of air heating by contact with the fins. The rate of air flow may be increased by utilizing a blower, such as a motor 47 and fan 48 positioned below the fins 44. The use of forced air cooling makes the operation of the system independent of ambient air motion in the room in which the light is being operated.

An opening-50 may .be-providedin the: upper surface of the block 20, in alignment with an opening 51 in the top of the box 10, for receiving a conventional bulb thermometer for measuring the temperature of the block. A cover plate 52 may be utilized to cover the opening 51 when the thermometer is not in use. i

The light source of the invention is intended for use with any .of the conventional vapor or gas discharge lamps, which are in general referred to as glow discharge lamps. A preferred form of lamp structure is illustrated in FIG. 5 and includes a glow discharge lamp which may be conventional in construction incorporating a lamp body 60 and abase .61. The improvement to be covered herein includes the addition of an outer sleeve 62 which is disposed about and spaced from the lamp body 60. The sleeve 62 is formed of a suitable'material, such as quartz, which will not adversely affect the lamp output. The sleeve 62 is carried on the base 61 and provides a closed space about the lamp body 60. In a typical structure, the sleeve 62 may be in the order of one-half inch diameter and the annular space about the lamp body 60 may be in the order of one-eighth inch thick and typically is filled with air.

I This lamp structure provides a number of advantages. The closed air space functions as an insulator, reducing heat flow from the lamp to the surrounding block thereby permitting maintenance of a higher lamp temperature with a lower power input. Glow discharge mercury lamps often generate a considerable amount of ozone around the periphery of the lamp. The ozone layer aifects the lamp radiation passing therethrough and variations in the thickness and density of the ozone layer due to air movement result in variations in intensity of the output. In the structure illustrated in FIG. 5, the space within the sleeve 62 becomes saturated with ozone, providing a nonmoving layer of ozone of fixed density and thickness, so that lamp intensity is not affected by ozone variation. Furthermore, the closed air space prevents direct air flow around the lamp 60, thereby eliminating temperature disturbances due to air motion. The base 61 preferably is formed of a material having a low heat conductivity, typically a molded plastic.

In operation of the light source, the block with its associated heater provides a control on the heat loss from the lamp itself. By maintaining the temperature of the block substantially constant, it is also possible to maintain the temperature of the lamp itself substantially constant although at a temperature greater than that of the block. The heat loss from the lamp to the block is relatively small, permitting operation of the lamp at higher temperatures with lower power input. The temperature of the block will be substantially uniform in the zone between the lamp and the heater and there will be a temperature gradient through the block between the heater and the cooling fins, but in general, the temperature at any particular point on the block is maintained substantially constant.

By wayof example, a light source constructed as shown in the drawing hereof with a UVP Model l1SC-1 Pen- Ray Lamp. has been operated for more than 100 hours. The block temperature was maintained constant within i /z F. and the lamp temperature was maintained within $0.1 F. of the set point during each operating period.

The emission intensity of the lamp. at .2537. Aw overua seven-hour test period varied less than i% Although an exemplary embodiment of the invention has been disclosed and discussed, it will be understood that other applications of the invention are possible and that the embodiment disclosed'rnay be subjected to various changes, modifications and substitutions without necessarily departingfrom the spirit of the invention. I claim as myin'vention:

1. In a stable light source for producingradiation at substantially constant intensity, the combination of:

a glowdischarge lamp; 5 a metal mounting block having a lamp opening therein with said lamp positioned in said lamp opening, said block including a light passage, communicating with said lamp. opening for permitting passage of i radiation from said lamp to the exterior of said bl'ock; a heater for said block; and I heater control means for energizing said heater from a power source, said control means including temperature responsive means carried on said block, said control means maintaining the temperature of said block adjacent said temperature responsive means substantially at a predetermined value intermediate.

that of said lamp and that of the ambient atmosphere. 2. A stable light source as defined in claim 1 in which said glow discharge lamp includes a lamp body and a base and an outer sleeve disposed about and spaced from said lamp body and carried on said base providing a closed space around said lamp body.

3. A stable light source as defined in claim 1 including cooling fins on said block remote from said lamp opening, with said heater and temperature responsive means positioned between said fins and said lamp opening, and means for moving atmospheric air past said fins.

4. A stable light source as defined in claim 1 in which said control means includes at least one transistor, and

with said transistor and temperature responsive means mounted in said block.

5. A stable light source as defined in claim 2 in which said mounting block includes a heater opening spaced from said lamp opening, with said heater positioned in.

said heater opening.

6. A stabilized light source as defined in claim 1 in WhlCh said heater control means maintains the temperature of said block adjacent said temperature responsive means at a predetermined value in the range of about 15 to 25 F. less than the temperature of said lamp.

References Cited JAMES w. LAWRENCE, Primary Examiner C. R. CAMPBELL, Assistant Examiner US. Cl X.R.

Shanks 313-25 X 

